Method of manufacturing an implosion-free television display tube



Aprll 23, 1.970 R. c. w. EISSES 3,508,310

METHOD OF MANUFACTURING AN IMPLOSION-FREE ,TELBVISION DISPLAY TUBE Filed June 20, 1968 INVENTOR -REINHART C. W.E|SSES United States Patent "ice 3 508 310 METHOD or MANUFACTURING AN IMPLOSION- FREE TELEVISION DISPLAY TUBE Reinhart Charles Willem Eisses, Emmasingel, Eindhoven,

Netherlands, assignors, by mesne assignments, to U.S. Philips Corporation, New York, N.Y., a corporation of Delaware Filed June 20, 1968, Ser. No. 738,553 Claims priority, application Netherlands, July 8, 1967, 6709525 Int. Cl. H011 9/18 U.S. Cl. 29-2513 2 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a method of manufacturing an implosion-free television display tube, in which the bulb of the tube is tightly surrounded by an annular band after at least the inner side of the band has been coated with a glue layer consisting of polyvinyl acetate, the space left between the bulb and the band then being filled with a hardening filler material. The invention further relates to a tube manufactured by this method.

When an annular band or hood is tightly fitted around the bulb of a display tube, the inner side of the band and preferably also the bulb itself are first coated with a glue layer of polyvinyl acetate, because it is of great importance that the filler material introduced into the space left between the band and the bulb should adhere satisfactorily both to the bulb and to the metal band. In order to ensure that also with bulbs of the minimum dimensions still lying within the tolerances, the annular band or hood tightly fits around the bulb, the dimensions of the band or hood must be chosen so as to match these minimum bulb dimensions, as a result of which with larger bulbs the annular band or hood must be pressed around the bulb with a comparatively large force.

This pressure force could be reduced by heating this band or hood, but the glue layer does not permit heating above 120 C. It is very uneconomical to choose the dimensions of the band so as to match the maximum bulb dimensions, since a large quantity or filler material is then required, while in the case of smaller bulbs, the band surrounds the bulb too loosely so that it may slip across the mould match line of the window and slide off the bulb, as the annular band is slipped around the bulb from the cone side until it abuts against the mold match junction. Heating above 120 C. appeared to be impermissible, since after cooling, the adherence betweenthe glue layer and the metal was found to have decreased to approximately However, pressing of the band or hood around the bulb involves the risk of the glue layer becoming damaged and the glass of the bulb to be scratched.

It is a surprise to find that this difiiculty can be avoided if, according to the invention, after the glue layer has dried, the annular band is heated to a temperature lying between 275 C. and 320 C. and is then slipped around 3,508,310 Patented Apr. 28, 1970 the bulb without pressing. It has been found that, after heating above 275 C., the adherence of the glue layer abruptly increases again and no longer decreases until it is heated to temperatures above 325 C. The invention takes advantage of this fact so that the strongly heated band can now he slipped around the bulb without any difficulty because at this higher temperature the expansion of the band or hood is sufiicient to neutralize the glass tolerances of the bulb, while the adherence between the glue layer and the metal remains sufiicient.

The invention will be described more fully with reference to the accompanying drawing, which is a sectional view part of a tube manufactured by the method described above.

In the drawing, reference numeral 1 denotes the window and reference numeral 2 the cone of a television display tube. From the cone side, an annular band 3 is slipped around the protruding edge of the window and the sealing seam between window 1 and cone 2. The band 3 is internally coated with a glue-layer 4 consisting of polyvinyl acetate. The bulb is also coated with such a glue layer 5.

After the glue layers 4 and 5 have dried, the band 3 is heated to 275 C. to 320 C. and is slipped around the bulb until it abuts against the shoulder of the mold match junction. After cooling, the remaining space is filled with a hardening filler material 6, preferably a polyester resin. If desired, the part of the bulb located between the annular band 3 and the display screen 9 may be left uncovered for reasons of mounting technology (smaller cabinet possible), in which event one or more further clamping bands 7 are arranged around the annular band 3 in order to increase the compressive force.

The cylindrical annular band 3 may also be replaced by a profiled band in the form of a hood partially enclosing the cone 2.

What is claimed is:

1. A method of manufacturing an implosion-free television display tube including an evacuated envelope having a window portion sealed to a conical portion and forming therewith a junction between the window portion and conical portion comprising the steps of coating at least the inner surface of an annular band, with a glue layer consisting of polyvinylacetate, drying the glue layer to set the polyvinylacetate, thereafter heating the so-coated annular band to a temperature between 275 C. and 320 C., placing the heated annular band around said junction of the envelope, cooling the annular band to shrink the same about the envelope placing the envelope under compressive stress while leaving a space between a portion of the band and the envelope, and filling the space between the annular band and the envelope with a hardenable filler material.

2. A method as claimed in claim 1, wherein the annular band has the shape of an annular hood.

References Cited UNITED STATES PATENTS 2,785,820 3/1957 Vincent. 3,220,593 11/1965 Powell et al.

3,278,682 10/1966 Panis et al.

JOHN F. CAMPBELL, Primary Examiner R. B. LAZARUS, Assistant Examiner U.S. Cl. X.R. 

